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Diffstat (limited to 'ffmpeg/libavformat/asfcrypt.c')
| -rw-r--r-- | ffmpeg/libavformat/asfcrypt.c | 185 |
1 files changed, 185 insertions, 0 deletions
diff --git a/ffmpeg/libavformat/asfcrypt.c b/ffmpeg/libavformat/asfcrypt.c new file mode 100644 index 0000000..a402758 --- /dev/null +++ b/ffmpeg/libavformat/asfcrypt.c @@ -0,0 +1,185 @@ +/* + * ASF decryption + * Copyright (c) 2007 Reimar Doeffinger + * This is a rewrite of code contained in freeme/freeme2 + * + * This file is part of FFmpeg. + * + * FFmpeg is free software; you can redistribute it and/or + * modify it under the terms of the GNU Lesser General Public + * License as published by the Free Software Foundation; either + * version 2.1 of the License, or (at your option) any later version. + * + * FFmpeg is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public + * License along with FFmpeg; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA + */ + +#include "libavutil/bswap.h" +#include "libavutil/common.h" +#include "libavutil/des.h" +#include "libavutil/intreadwrite.h" +#include "libavutil/rc4.h" +#include "asfcrypt.h" + +/** + * @brief find multiplicative inverse modulo 2 ^ 32 + * @param v number to invert, must be odd! + * @return number so that result * v = 1 (mod 2^32) + */ +static uint32_t inverse(uint32_t v) +{ + // v ^ 3 gives the inverse (mod 16), could also be implemented + // as table etc. (only lowest 4 bits matter!) + uint32_t inverse = v * v * v; + // uses a fixpoint-iteration that doubles the number + // of correct lowest bits each time + inverse *= 2 - v * inverse; + inverse *= 2 - v * inverse; + inverse *= 2 - v * inverse; + return inverse; +} + +/** + * @brief read keys from keybuf into keys + * @param keybuf buffer containing the keys + * @param keys output key array containing the keys for encryption in + * native endianness + */ +static void multiswap_init(const uint8_t keybuf[48], uint32_t keys[12]) +{ + int i; + for (i = 0; i < 12; i++) + keys[i] = AV_RL32(keybuf + (i << 2)) | 1; +} + +/** + * @brief invert the keys so that encryption become decryption keys and + * the other way round. + * @param keys key array of ints to invert + */ +static void multiswap_invert_keys(uint32_t keys[12]) +{ + int i; + for (i = 0; i < 5; i++) + keys[i] = inverse(keys[i]); + for (i = 6; i < 11; i++) + keys[i] = inverse(keys[i]); +} + +static uint32_t multiswap_step(const uint32_t keys[12], uint32_t v) +{ + int i; + v *= keys[0]; + for (i = 1; i < 5; i++) { + v = (v >> 16) | (v << 16); + v *= keys[i]; + } + v += keys[5]; + return v; +} + +static uint32_t multiswap_inv_step(const uint32_t keys[12], uint32_t v) +{ + int i; + v -= keys[5]; + for (i = 4; i > 0; i--) { + v *= keys[i]; + v = (v >> 16) | (v << 16); + } + v *= keys[0]; + return v; +} + +/** + * @brief "MultiSwap" encryption + * @param keys 32 bit numbers in machine endianness, + * 0-4 and 6-10 must be inverted from decryption + * @param key another key, this one must be the same for the decryption + * @param data data to encrypt + * @return encrypted data + */ +static uint64_t multiswap_enc(const uint32_t keys[12], + uint64_t key, uint64_t data) +{ + uint32_t a = data; + uint32_t b = data >> 32; + uint32_t c; + uint32_t tmp; + a += key; + tmp = multiswap_step(keys, a); + b += tmp; + c = (key >> 32) + tmp; + tmp = multiswap_step(keys + 6, b); + c += tmp; + return ((uint64_t)c << 32) | tmp; +} + +/** + * @brief "MultiSwap" decryption + * @param keys 32 bit numbers in machine endianness, + * 0-4 and 6-10 must be inverted from encryption + * @param key another key, this one must be the same as for the encryption + * @param data data to decrypt + * @return decrypted data + */ +static uint64_t multiswap_dec(const uint32_t keys[12], + uint64_t key, uint64_t data) +{ + uint32_t a; + uint32_t b; + uint32_t c = data >> 32; + uint32_t tmp = data; + c -= tmp; + b = multiswap_inv_step(keys + 6, tmp); + tmp = c - (key >> 32); + b -= tmp; + a = multiswap_inv_step(keys, tmp); + a -= key; + return ((uint64_t)b << 32) | a; +} + +void ff_asfcrypt_dec(const uint8_t key[20], uint8_t *data, int len) +{ + struct AVDES des; + struct AVRC4 rc4; + int num_qwords = len >> 3; + uint8_t *qwords = data; + uint64_t rc4buff[8] = { 0 }; + uint64_t packetkey; + uint32_t ms_keys[12]; + uint64_t ms_state; + int i; + if (len < 16) { + for (i = 0; i < len; i++) + data[i] ^= key[i]; + return; + } + + av_rc4_init(&rc4, key, 12 * 8, 1); + av_rc4_crypt(&rc4, (uint8_t *)rc4buff, NULL, sizeof(rc4buff), NULL, 1); + multiswap_init((uint8_t *)rc4buff, ms_keys); + + packetkey = AV_RN64(&qwords[num_qwords * 8 - 8]); + packetkey ^= rc4buff[7]; + av_des_init(&des, key + 12, 64, 1); + av_des_crypt(&des, (uint8_t *)&packetkey, (uint8_t *)&packetkey, 1, NULL, 1); + packetkey ^= rc4buff[6]; + + av_rc4_init(&rc4, (uint8_t *)&packetkey, 64, 1); + av_rc4_crypt(&rc4, data, data, len, NULL, 1); + + ms_state = 0; + for (i = 0; i < num_qwords - 1; i++, qwords += 8) + ms_state = multiswap_enc(ms_keys, ms_state, AV_RL64(qwords)); + multiswap_invert_keys(ms_keys); + packetkey = (packetkey << 32) | (packetkey >> 32); + packetkey = av_le2ne64(packetkey); + packetkey = multiswap_dec(ms_keys, ms_state, packetkey); + AV_WL64(qwords, packetkey); +} |